Seeing the aura is a matter of taking your eyes slightly out of focus. If you've ever been able to see those holographic picture-in-a-picture things then you shouldn't have any trouble seeing auras as you do exactly the same thing with your eyes.
The first time I was at a seminar and this topic came up I had no luck whatsoever with seeing the auras of the other folks in the seminar. That night I went over to the bookstore and grabbed a bunch of the holograph picture books and sat there til I could relax my eyes and see them. The next day when I went back for the rest of the seminar I didn't have any trouble seeing the auras of the other attendees.
Have your training partner stand in front of a light-colored wall in a dimly lit room. Have your partner hold one finger in front of their face, about 6 inches out from their chin.
Now focus your eyes on their finger, not their face. Have them remove their fingers but keep looking at the same spot. You'll have to relax your eyes a bit to do this. Now, using that same relaxed vision, if you look at them you should be able to see what looks like a little line that runs all around them a couple of inches out from their body.
The next layer out is even more faint and may have colors associated with it. The different meanings of the colors vary widely depending on who you're talking to. My advice in this area is to open up your awareness and see for yourself which colors seem to be associated most often with which types of people and their behaviors.
Play with this a bit. Does their aura change when they think happy thoughts? Sad thoughts? Angry thoughts?
Some people can see auras instantly and others have to work at it. Don't be too put out if it takes a while. As you work with this you'll gradually become aware of even more subtle layers of energy that surround people. You may also find that you can actually feel another person's chakras and even discern which is their dominant chakra, which tells you instantly how that person is likely to react to any given stimuli.